Convert Square Miles to Acres (mi2 to ac)
1 square mile (mi²) = 640 acres (ac). 1 ac = 0.0015625 mi². Example: 15 mi² = 15 × 640 = 9600 ac.
Also searched as square miles to ac, square miles in ac, square miles into acres, mi2 to ac, mi2 in acres, mi2 into acre, square mile to acre, mi2 to acres converter and how many acres in a square mile.
1 mi² = 640 ac
Type in either box. Scientific notation works: 1.5e-3.
Converting a list? Use the bulk square mile to acre converter to paste a column from Excel.
How to Convert Square Mile to Acre
- 1 mi² = 640 ac
- 1 ac = 0.0015625 mi²
- Example: convert 15 mi² to ac: 15 mi² = 15 × 640 ac = 9600 ac
Formula
ac = mi² × 640
Derivation from SI units:
- 1 mi² = (1609.344 m)² = 2 589 988.110336 m² = 640 acres
- 1 acre = 43 560 ft² = 4 046.856 422 4 m² (international foot; the US survey foot was retired at the end of 2022)
- 1 mi² = 2589988.110336 m² ÷ 4046.8564224 m² per ac = 640 ac
Both units are defined exactly, so the factor is exact. Square Mile definition: square mile; Acre definition: acre.
Worked examples
- A reading of 2 mi² converts to 1280 ac.
2 mi² × 640 = 1280 ac - A value of 25 mi² is 16000 ac.
25 mi² × 640 = 16000 ac
Square Mile to Acre conversion table
| Square Miles (mi²) | Acres (ac) |
|---|---|
| 0.1 mi² | 64 ac |
| 0.5 mi² | 320 ac |
| 1 mi² | 640 ac |
| 2 mi² | 1280 ac |
| 5 mi² | 3200 ac |
| 10 mi² | 6400 ac |
| 25 mi² | 16000 ac |
| 50 mi² | 32000 ac |
| 100 mi² | 64000 ac |
| 1000 mi² | 640000 ac |
Where it's used
Square Miles are used for US city and county areas, while acres appear in US, UK and Indian land and property listings. Both measure area, so the conversion is a fixed factor.
Square Mile to other area units
| Conversion | 1 mi² equals |
|---|---|
| square mile to acre | 640 ac |
| square mile to square meter | 2589988.11 m² |
| square mile to square centimeter | 25899881100 cm² |
| square mile to square foot | 27878400 ft² |
| square mile to square inch | 4014489600 in² |
| square mile to hectare | 258.998811 ha |
| square mile to square millimeter | 2589988110000 mm² |
| square mile to square kilometre | 2.58998811 km² |
Show 1 more units
| square mile to square yard | 3097600 yd² |
|---|
Frequently asked questions
How many acres are in 1 square mile?
1 mi² = 640 ac.
How do I convert square miles to acres?
Multiply the value in mi² by 640. For example, 15 mi² × 640 = 9600 ac.
Is the mi² to ac conversion exact?
Yes. Both units are defined exactly, and 1 mi² is exactly 640 ac.
Sources
- Guide for the Use of the International System of Units (SI), NIST Special Publication 811, 2008 Edition, National Institute of Standards and Technology , Appendix B.8, "square mile (mi²)".
- NIST Handbook 44, Appendix C: General Tables of Units of Measurement, National Institute of Standards and Technology , Appendix C, units of area.
Last reviewed: . Factors are stored exactly and computed with 50-digit decimal arithmetic. See how we verify conversion factors.
Cite this page
APA
Scientific Converters. (2026, October 15). Convert Square Miles to Acres (mi2 to ac). Retrieved October 25, 2026, from https://scientificconverters.com/area/square-miles-to-acres/
IEEE
Scientific Converters, "Convert Square Miles to Acres (mi2 to ac)," scientificconverters.com. Accessed: Oct. 25, 2026. [Online]. Available: https://scientificconverters.com/area/square-miles-to-acres/